2 files changed, 74 insertions, 6 deletions

diff --git a/src/corelib/kernel/qeventdispatcher_win.cpp b/src/corelib/kernel/qeventdispatcher_win.cpp
index b55679f3d5..6da70cf0bd 100644
--- a/src/corelib/kernel/qeventdispatcher_win.cpp
+++ b/src/corelib/kernel/qeventdispatcher_win.cpp
@@ -561,6 +561,17 @@ static HWND qt_create_internal_window(const QEventDispatcherWin32 *eventDispatch
     return wnd;
 }
 
+static void calculateNextTimeout(WinTimerInfo *t, quint64 currentTime)
+{
+    uint interval = t->interval;
+    if ((interval >= 20000u && t->timerType != Qt::PreciseTimer) || t->timerType == Qt::VeryCoarseTimer) {
+        // round the interval, VeryCoarseTimers only have full second accuracy
+        interval = ((interval + 500)) / 1000 * 1000;
+    }
+    t->interval = interval;
+    t->timeout = currentTime + interval;
+}
+
 void QEventDispatcherWin32Private::registerTimer(WinTimerInfo *t)
 {
     Q_ASSERT(internalHwnd);
@@ -568,6 +579,7 @@ void QEventDispatcherWin32Private::registerTimer(WinTimerInfo *t)
     Q_Q(QEventDispatcherWin32);
 
     int ok = 0;
+    calculateNextTimeout(t, qt_msectime());
     uint interval = t->interval;
     if (interval == 0u) {
         // optimization for single-shot-zero-timer
@@ -576,17 +588,13 @@ void QEventDispatcherWin32Private::registerTimer(WinTimerInfo *t)
     } else if ((interval < 20u || t->timerType == Qt::PreciseTimer) && qtimeSetEvent) {
         ok = t->fastTimerId = qtimeSetEvent(interval, 1, qt_fast_timer_proc, (DWORD_PTR)t,
                                             TIME_CALLBACK_FUNCTION | TIME_PERIODIC | TIME_KILL_SYNCHRONOUS);
-    } else if (interval >= 20000u || t->timerType == Qt::VeryCoarseTimer) {
-        // round the interval, VeryCoarseTimers only have full second accuracy
-        interval = ((interval + 500)) / 1000 * 1000;
     }
+
     if (ok == 0) {
         // user normal timers for (Very)CoarseTimers, or if no more multimedia timers available
         ok = SetTimer(internalHwnd, t->timerId, interval, 0);
     }
 
-    t->timeout = qt_msectime() + interval;
-
     if (ok == 0)
         qErrnoWarning("QEventDispatcherWin32::registerTimer: Failed to create a timer");
 }
@@ -611,6 +619,9 @@ void QEventDispatcherWin32Private::sendTimerEvent(int timerId)
         // send event, but don't allow it to recurse
         t->inTimerEvent = true;
 
+        // recalculate next emission
+        calculateNextTimeout(t, qt_msectime());
+
         QTimerEvent e(t->timerId);
         QCoreApplication::sendEvent(t->obj, &e);
 
diff --git a/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp b/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
index c7011dbc04..1d1432f600 100644
--- a/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
+++ b/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
@@ -54,6 +54,8 @@ private slots:
     void singleShotTimeout();
     void timeout();
     void remainingTime();
+    void remainingTimeDuringActivation_data();
+    void remainingTimeDuringActivation();
     void livelock_data();
     void livelock();
     void timerInfiniteRecursion_data();
@@ -79,14 +81,16 @@ class TimerHelper : public QObject
 {
     Q_OBJECT
 public:
-    TimerHelper() : QObject(), count(0)
+    TimerHelper() : QObject(), count(0), remainingTime(-1)
     {
     }
 
     int count;
+    int remainingTime;
 
 public slots:
     void timeout();
+    void fetchRemainingTime();
 };
 
 void TimerHelper::timeout()
@@ -94,6 +98,12 @@ void TimerHelper::timeout()
     ++count;
 }
 
+void TimerHelper::fetchRemainingTime()
+{
+    QTimer *timer = static_cast<QTimer *>(sender());
+    remainingTime = timer->remainingTime();
+}
+
 void tst_QTimer::zeroTimer()
 {
     TimerHelper helper;
@@ -158,6 +168,53 @@ void tst_QTimer::remainingTime()
 
     int remainingTime = timer.remainingTime();
     QVERIFY2(qAbs(remainingTime - 150) < 50, qPrintable(QString::number(remainingTime)));
+
+    // wait for the timer to actually fire now
+    connect(&timer, SIGNAL(timeout()), &QTestEventLoop::instance(), SLOT(exitLoop()));
+    QTestEventLoop::instance().enterLoop(5);
+    QVERIFY(!QTestEventLoop::instance().timeout());
+    QCOMPARE(helper.count, 1);
+
+    // the timer is still active, so it should have a non-zero remaining time
+    remainingTime = timer.remainingTime();
+    QVERIFY2(remainingTime > 150, qPrintable(QString::number(remainingTime)));
+}
+
+void tst_QTimer::remainingTimeDuringActivation_data()
+{
+    QTest::addColumn<bool>("singleShot");
+    QTest::newRow("repeating") << true;
+    QTest::newRow("single-shot") << true;
+}
+
+void tst_QTimer::remainingTimeDuringActivation()
+{
+    QFETCH(bool, singleShot);
+
+    TimerHelper helper;
+    QTimer timer;
+
+    const int timeout = 20;     // 20 ms is short enough and should not round down to 0 in any timer mode
+
+    connect(&timer, SIGNAL(timeout()), &helper, SLOT(fetchRemainingTime()));
+    connect(&timer, SIGNAL(timeout()), &QTestEventLoop::instance(), SLOT(exitLoop()));
+    timer.start(timeout);
+    timer.setSingleShot(singleShot);
+
+    QTestEventLoop::instance().enterLoop(5);
+    QVERIFY(!QTestEventLoop::instance().timeout());
+    if (singleShot)
+        QCOMPARE(helper.remainingTime, -1);     // timer not running
+    else
+        QCOMPARE(helper.remainingTime, timeout);
+
+    if (!singleShot) {
+        // do it again - see QTBUG-46940
+        helper.remainingTime = -1;
+        QTestEventLoop::instance().enterLoop(5);
+        QVERIFY(!QTestEventLoop::instance().timeout());
+        QCOMPARE(helper.remainingTime, timeout);
+    }
 }
 
 void tst_QTimer::livelock_data()